KR910003068B1 - Reinforcing fibrous material - Google Patents

Abstract

Reinforcing fibrous material having an improved adhesion, consists essentially of a surface-treated, molecularly oriented, silane-crosslinked ultra-high-molecular-weight polyethylene fibre, wherein the measurement is conducted under restraint conditions by using a differential scanning calorimeter, the crosslinked polyethylene fibre has at least two crystal melting peaks (Tp) at temperatures higher by at least 10 DEG C than the inherent crystal melting temperature (Tm) of the ultra-high-molecular-weight polyethylene determined as the main peak at the time of the second temperature elevation, the heat of fusion based on these crystal melting peaks (Tp) is at least 50% of the whole heat of fusion, and the sum of heat of fusion of high-temperature side peaks (Tp1) at temperatures in the range of from (Tm + 35) DEG C to (Tm + 120) DEG C is at least 5% of the whole heat of fusion, and wherein the crosslinked polyethylene fibre has a surface containing at least 8 carbon atoms, especially at least 10 carbon atoms, per 100 carbon atoms, as determined by the electron spectroscopy for chemical analysis.

Description

Fiber material for reinforcement

1 is a graph showing the melting characteristic curves of crosslinked filaments after silane graft and stretching of ultra high molecular weight polyethylene.

FIG. 2 is a graph showing the melting characteristic curve of the sample of FIG. 1 at the second temperature measurement. FIG.

3 is an electron micrograph (1000 times) of surface-treated molecular alignment and silane crosslinked ultra high molecular weight polyethylene fiber surface,

4 is an electron micrograph (1000 times) of the untreated unna orientation and silane crosslinked ultra high molecular weight polyethylene fiber surface,

5 is a graph showing the creep properties of molecular orientation and silane crosslinked ultrahigh molecular weight polyethylene fibers of Example 1. FIG.

The present invention relates to a reinforcing fiber, and more particularly, a reinforcing fiber which is excellent in combination of adhesion and creep resistance to a matrix of surface-treated molecular alignment and silane crosslinked ultra high molecular weight polyethylene fibers and which can significantly improve the strength of the composite. It is about.

Fiber-reinforced plastics are widely used in automobile parts, electric appliance parts, housings, industrial materials, small ships, sporting goods, medical materials, civil engineering materials, and building materials because of their excellent strength and rigidity. However, since most of the fiber reinforcing materials used therein are glass fibers, the resulting composite material is heavier than unreinforced plastics, and thus, a composite material having light and good mechanical strength is desired.

On the other hand, polyolefins such as high-density polyethylene, and filaments drawn from ultra-high molecular weight polyethylene at high magnification, have high elasticity, high strength, and are lightweight, and are thus expected to be a fiber reinforcing material suitable for lightening composite materials.

However, polyolefins have poor adhesion to matrices, such as resins and rubbers, and polyolefins, in particular, polyethylenes, have difficulty in heat resistance and creep easily at relatively low temperatures.

Plasma discharge treatment of a polyolefin molded article as a means of improving adhesiveness (Ag. 54-794, 57-177032) or Corona discharge treatment of a polyolefin molded article and The method of improving the adhesiveness of the (JP-A-58-5314, JP-A-60-146078) etc. was proposed. The development of adhesion improvement by such a method is characterized by the fact that many fine particles of 0.1-4μ are formed on the surface of the polyolefin molded article as described in Japanese Patent Application Laid-Open Nos. 57-177032 and 58-5314. Thus, it is described that the adhesion of the surface of the molded article is improved. Further, in the above publication No. 60-146078, it is essential that a very fine haze due to discharge on the filament is generated even when performing a corona discharge treatment in which the total irradiation dose is weakened to 0.05-3.0 watt minute / m2. As a result, the tensile strength of the filament is reduced by 60-70% compared to the untreated product only by performing a corona discharge treatment of 0.2 W.min / m 2, where the total amount of irradiation is slightly small. As shown in the first table, the cause of the decrease in strength is presumed to be due to the minute occurrence occurring on the front surface.

The improvement of the adhesiveness of the polyolefin fibers seen in the prior art is due to the formation of fine particles on the surface of the fiber and the increase of the specific adhesion surface area or the anchoring effect, but the mechanical strength of the fiber itself is reduced by such treatment. Inevitably, the composites reinforced with these fibers are not satisfactory in mechanical properties such as bending strength.

The present inventors have first extruded after grafting a silane compound in the presence of radical initiator in ultra high molecular weight polyethylene having an extreme viscosity {η} of 5dl / g or more, and then impregnating a silanol condensation catalyst after stretching or extruding the extrudate. After crosslinking by exposure to moisture, a novel molecularly oriented molded article can be obtained in which the oriented phenomenon of melting temperature, which is not seen at all in conventional stretched or crosslinked molded articles of polyethylene, is obtained. It was found that even when exposed for 10 minutes, the shape of the stretched molded product was not melted and the high strength retention was maintained even after this heat history. In addition, the stretched molded article was found to have a high elastic modulus and a high tensile strength unique to the ultra-high molecular weight polyethylene stretched mold, and significantly improved the creep resistance.

The present inventors, in turn, perform surface treatment such as plasma treatment or corona treatment on the molecular orientation and silane-crosslinked ultra high molecular weight polyethylene fibers, without impairing the mechanical properties and creep resistance of the fibers. It has been found that the adhesion to the matrix of the present invention can be significantly improved and the strength of the composite can be improved.

According to the present invention, it becomes a fiber of surface-treated molecular orientation and silane crosslinked ultrahigh molecular weight polyethylene, and the fiber is inherently crystallized in ultrahigh molecular weight polyethylene which is obtained as a main melting peak at the second temperature rise when measured by a differential scanning calorimeter in a confined state. At least two crystal melting peaks (Tp) at a temperature of at least 10 ° C higher than the temperature (Tm) and at the same time, the amount of heat of fusion corresponding to the crystal melting peak (Tp) per heat of melting is 50% or more and the temperature range Tm + 35 ° C-Tm The total amount of heat of fusion based on the high-temperature melting peak (Tp1) at + 120 ° C is 5% or more per melting amount, and this fiber is measured by electron spectroscopy pore chemical analysis (ESCA) per 100 carbon atoms. A reinforcing fiber material having improved adhesion is characterized by having a surface having a composition having at least eight, in particular ten or more oxygen atoms.

According to the present invention, when molecular orientation and silane crosslinked ultrahigh molecular weight polyethylene fibers are selected as the fiber substrates to be treated and subjected to surface treatment such as plasma treatment or corona discharge treatment, the matrix of resins or the like is not degraded. According to the knowledge that can significantly improve the adhesion with.

In other words, according to the teaching of the prior art, when the polyethylene fiber is subjected to prisma treatment or corona discharge treatment, microfibers (fitting) are generated on the entire surface of the fiber, thereby improving adhesion to the matrix. By using the orientation and silane crosslinked ultra high molecular weight polyethylene fibers as a gas, such fittings do not occur, and the fiber surface is smooth and oxygen is bonded to the surface to improve adhesion. Since the fiber has the same smooth surface as the original fiber, the strength and elastic modulus of the fiber itself are hardly reduced, and further, since the fiber base is excellent in heat resistance and creep resistance, it is possible to impart this excellent property to the fiber reinforced composite.

In the present invention, the molecular orientation and silane crosslinked ultra high molecular weight polyethylene fibers used as the gas refers to a fiber in which silane graft ultra high molecular weight polyethylene fibers are molecularly aligned by stretching and then silane crosslinked. In other words, when the silane graft ultrahigh molecular weight polyethylene is stretched, the silane graft portion is selectively non-fixed, and an oriented crystal part is generated through the non-fixed portion. Subsequently, when the stretched product is crosslinked in the presence of a silanol condensation catalyst, a crosslinked structure is selectively formed at non-government, and a structure in which both ends of the alignment crystal part are fixed by silane crosslinking is obtained. This molecular orientation and silane crosslinking structure have significant advantages in the heat and creep resistance of the fiber reinforcement, but in the prevention of fittings during surface treatment.

FIG. 1 shows an endothermic curve by differential scanning calorimetry measured under constraint conditions for molecular alignment and silane crosslinked polyethylene fibers used in the present invention. The endothermic curve was shown when the second run of FIG. 1 (the second temperature rise measurement after FIG. 1 performed the measurement) was performed. In addition, the term "constraints" in the present specification refers to a condition in which the end is fixed so that free deformation is prevented even though the molded body is not actively tensioned.

As evident in these figures, the fibers used in the present invention have at least two crystal melting peaks (Tp) at a temperature at least 10 ° C. higher than the original crystal melting temperature (Tm) of ultra high molecular weight polyethylene, and furthermore, crystal melting per calorie melting amount. The heat of fusion according to the peak TP is 50% or more, particularly 60% or more. The crystal melting peak (Tp) has a high temperature side melting peak (Tp1) in the temperature range Tm + 35 ° C-Tm + 120 ° C and a low temperature side peak (Tp2) in the temperature range Tm + 10 ° C-Tm + 35 ° C. Although it may be expressed in two ways, the total amount of heat of fusion based on Tp1 is 5% or more, especially 10% or more, per heat of fusion in the fiber of the present invention.

These high crystal melting peaks (Tp1, Tp2) act to remarkably improve the heat resistance of ultra high molecular weight polyethylene molded articles, but it is the high temperature side melting peak (Tp1) that contributes to the improvement of strength retention after high temperature thermal history. do.

That is, in the molecular orientation silane crosslinked fiber of the present invention, since the crystal melting temperature of at least part of the polymer chain constituting the fiber is shifted to a very high temperature side as described above, it is extremely excellent in heat resistance and a thermal history for 10 minutes at 160 ° C. The strength retention rate after giving the heat retention is preferably 80% or more, preferably the strength retention rate after giving the heat history for 10 minutes at 180 ° C. for 60 minutes or more, especially 80% or more and 5 minutes at 200 ° C. for 5 minutes. From this ultra high molecular weight polyethylene of more than 80%, it is surprisingly unpredictable.

The fiber of the present invention exhibits elongation of at least 50% after 1 minute of uncrosslinked material under heat creep characteristics such as load: 30% breaking load and temperature: 70 ° C. Very good at over 20%.

The fiber of the present invention exhibits 20% or less of elongation after standing for 1 minute while uncrosslinked material is elongated to rupture without waiting for 1 minute under load: 50% breaking load and temperature: 70 ° C.

FIG. 3 is a surface electron micrograph (1000 times magnification) of the molecular orientation and silane crosslinked surface treatment (Example 1) according to the present invention, and FIG. 4 is a molecular orientation and silane crosslinking without surface treatment. The same surface electron micrograph of ultra high molecular weight polyethylene fibers. Surface imaging is performed under the following conditions after the next pretreatment. That is, in pretreatment, (1) the cover glass is fixed to a sample stand with a double-sided tape, and a sample is fixed with a double-sided tape on it.

(2) A conductive paint (silver paste, Sylvest P-225) is applied between the sample stand and the sample, and the cover glass and sample stand.

(3) Vacuum is deposited on the sample surface using Nippon Denshi Co., Ltd. JEE 4B. Moreover, photography is performed at 1000 times magnification with JSM 25 S111 by Nihon Denshi Corporation. The acceleration voltage at this time is performed at 12.5 KV.

From the results of FIGS. 3 and 4, it is clear that the surface-treated fibers according to the present invention have a smooth surface, and the fact that the crack width in the orientation direction does not form on the surface in a size of 0.1 µm or more, particularly 0.08 µm or more. It is obvious. In other words, the mechanical strength of the polyethylene fiber having a width of 0.1 µm or more formed on the surface is considerably lowered. In the fiber of the present invention, the crack width is suppressed to less than 0.1 µm, so that the mechanical strength substantially the same as that of the treatment line is maintained even after treatment. will be.

The surface-treated fibers used in the present invention are characterized by at least 8, preferably 10 or more, atoms of oxygen atoms per 100 carbon atoms measured on the surface by ESCA.

That is, the number of oxygen atoms added to the untreated molecular orientation and silane crosslinked polyethylene polymer fibers is less than seven per C100. In the fibers of the present invention, the number of oxygen atoms added to the above range is increased, and thus, Adhesiveness is remarkably increased. In addition number of oxygen atoms × ray photoelectron spectrometer used (Shimadzu Seisakusho claim ESCA750 type), and the degree of vacuum by introducing the sample for the sample was fixed with double-sided tape, then to 10 ^-8 Torr as the light source Al K α (1,486,6 eV) was used to measure C ¹⁵ and O ¹⁵ . After the measurement, waveform processing was performed, and the respective peak areas were calculated to determine the amount of oxygen to carbon.

In the above description, it is evident that the adhesion improvement in the molecular orientation and silane crosslinked ultrahigh molecular polyethylene fibers treated by the present invention is due to the addition of oxygen atoms on the surface, not the formation of fittings on the fiber surface. The reason is that the molecular orientation and the silane crosslinking structure in the fiber substrate prevent the formation of the fitting during the plasma treatment or the corona discharge treatment, but allow the oxidation treatment.

The reinforcing fiber material of the present invention is a molecular orientation fiber formed by forming a silane graft ultra high molecular weight polyethylene into a fibrous form and stretching it, and the molecular orientation fiber obtained by silane crosslinking in the presence of a silanol condensation catalyst It is obtained by performing a plasma treatment or a corona discharge treatment.

The ultrahigh molecular weight polyethylene (A) used in the present invention has an intrinsic viscosity {eta} in the decalin solvent of 135 ° C of 5 dl / g or more, preferably in the range of 7 to 30 dl / g.

If {η} is less than 5 dl / g, a stretched product having excellent tensile strength will not be obtained even if the draw ratio is increased. In addition, the upper limit of {η} is not particularly limited, but a value of more than 30 dl / g tends to be extremely high in melt viscosity under high concentration and to melt melt in compression, resulting in poor melt spinning. Such ultra high molecular weight polyethylene is polyethylene obtained by polymerizing ethylene or ethylene with a small amount of other α-olefins such as propylene, 1-butene, 4-methyl-1-pentene, 1-hexane, etc. by so-called Ziegler polymerization. The thing of the range with high molecular weight among them.

The silane compound which can be used for the graft treatment may be any silane compound capable of graft treatment and crosslinking treatment. Such a silane compound has both a radical polymerizable organic group and a hydrolyzable organic group.

In the market, R is an organic group including radically polymerizable ethylene-based unsaturation, Y is a hydrolyzable organic group and n is a number of 1 or 2. Is displayed.

Examples of the radically polymerizable organic group include alkyl groups containing ethylenically unsaturated hydrogen groups such as vinyl group, aryl group, butenyl group, and cyclohexenyl group, and ethylenically unsaturated carboxylic acid ester units such as acryloxy alkyl group and methacryloxy alkyl group. Vinyl groups are suitable. As an organic group which can be hydrolyzed, an alkoxy group, an acyloxy group, etc. are mentioned.

Suitable examples of the silane compound include, but are not limited to, vinyl triethoxysilane, vinyl trimethoxysilane, vinyl tris (methoxy ethoxy) silane, and the like.

According to the present invention, the composition containing the ultra high molecular weight polyethylene, the silane compound, the radical initiator and the diluent is thermoformed by melt extrusion or the like, thereby forming the silane graft and the fiber. That is, polymer radicals are generated in the ultrahigh molecular weight polyethylene by the action of the radical initiator and heat during melt kneading, and graft of the silane compound into the ultrahigh molecular weight polyethylene is generated by the reaction between the polymer radical and the silane compound.

As a radical initiator, all the radical initiators used for this kind of graft processing can be used, For example, an organic peroxide, an organic perester, an azo compound etc. are used. In order to perform graft effectively under the melt kneading conditions of ultra high molecular weight polyethylene, it is preferable to exist in the range of the half life temperature 100-200 degreeC of a radical initiator.

In the present invention, a diluent is formulated to enable melt molding of the silane graft ultra high molecular weight polyethylene. As such a diluent, solvents for ultra high molecular weight polyethylene or various waxy substances having compatibility with ultra high molecular weight polyethylene are used.

The solvent is preferably a solvent having a melting point of the polyethylene above, more preferably a boiling point of + 20 ° C. or higher, and for example, an aliphatic hydrocarbon solvent, an aromatic hydrocarbon solvent or a hydrogenated derivative halogenated hydrocarbon solvent. .

As the wax, an aliphatic hydrocarbon compound or a derivative thereof is used. The aliphatic hydrocarbon compound is mainly composed of a saturated aliphatic hydrocarbon compound, and usually has a molecular weight of 2000 or less, preferably 1000 or less, and more preferably 800 or less, called a paraffin wax. As the aliphatic hydrocarbon compound derivative, for example, one or more, preferably 1 to 2, particularly preferably 1 carboxyl group, hydroxyl group, carbamoyl group at the terminal or inside of the aliphatic hydrocarbon group (alkyl group, alkenyl group) , Aliphatic, aliphatic alcohols, aliphatic amides, fatty acid esters having 8 or more carbon atoms, preferably 12-50 carbon atoms or 130-2000 molecular weights, preferably 200-800, which are compounds having functional groups such as ester groups, mercapto groups and carbonyl groups And aliphatic mercaptans, aliphatic aldehydes, and aliphatic ketones.

In the present invention, it is particularly preferable to use waxes as diluents. This is because the composition for extrusion is easily obtained by kneading in a relatively short time by the use of waxes, and the sensitivity of polyethylene which causes the fitting is suppressed.

In the present invention, the silane compound per 100 parts by weight of the ultra high molecular weight polyethylene is 0.1 to 10 parts by weight, in particular 0.2 to 5.0 parts by weight, the radical initiator is generally 0.01 to 3.0 parts by weight, especially 0.05 to 0.5 parts by weight and the diluent is 9900 to 33 It is preferred to use in parts by weight, in particular 1900 to 100 parts by weight. When the amount of the silane compound is lower than the above range, the crosslinking density of the final stretched crosslinking molding agent is too low, so that the desired crystal melting temperature is not improved. On the other hand, when the amount of the silane compound exceeds the above range, there is a tendency that the crystallinity of the final crosslinked product is lowered, and the mechanical properties, that is, the elastic modulus and the tensile strength, are lowered. In addition, the silane compound is expensive and disadvantageously economically. When the amount of the diluent is lower than the above range, the melt viscosity becomes too high to make melt kneading and melt molding difficult, and the roughness of the surface of the fiber is severe, and the stretching is likely to occur. On the other hand, when the amount of the diluent is larger than the above range, melt kneading is also difficult and the stretchability of the molded article is inferior.

The compounding of each of the above chemicals into ultra high molecular weight polyethylene can be carried out by any means. The silane compound, the radical initiator and the diluent may be simultaneously mixed and melt kneaded, or the silane compound and the radical initiator may be first mixed, followed by the diluent, or conversely, the ultra high molecular weight polyethylene may be first mixed with the silane compound and The method of mix | blending a radical initiator etc. is used.

Melt kneading is generally performed at a temperature of 150 to 300 ° C., especially 170 to 270 ° C., and melting temperature is too high at a temperature lower than the above range, making melt molding difficult, and when higher than the above range, it is very high due to thermal sensitivity. Molecular weight The molecular weight of polyethylene falls, and it becomes difficult to obtain a molded article having a high modulus of elasticity and high strength. The mixing may be carried out by a dry brand using a Henschel mixer, a V-type brander or the like, or may be performed by melt mixing using a single screw or a multi screw extruder.

Stretching filaments are obtained by performing extrusion with a spinning nozzle, but a draft, that is, stretching in a molten state, may be added to the melt extruded from the spinning nozzle. The ratio between the extrusion speed in the die orifice of the molten resin and the winding speed V between the Vo and the uncured and uncured unstretched material can be defined as the draft ratio.

Such a draft ratio is usually 3 or more, preferably 6 or more, depending on the temperature of the mixture and the molecular weight of the ultrahigh molecular weight polyethylene.

The cooling solidification of the molded filament can be performed by forced cooling means such as air cooling or water cooling.

The unstretched fiber of the silane graft ultra high molecular weight polyethylene obtained in this way is extended | stretched. The degree of stretching treatment is, of course, to effectively impart molecular orientation in the uniaxial direction to the ultra high molecular weight polyethylene of the fiber.

Stretching of the silane graft polyethylene filament is generally performed at a temperature of 40 to 160 ° C, in particular 80 to 145 ° C. As a heat medium for heating and holding an unstretched fiber at the said temperature, any of air, water vapor, and a liquid medium can be used.

However, as the heat medium, the above-mentioned diluent is a solvent capable of eluting and removing, and the boiling point is higher than the melting point of the molded body composition, specifically, when the stretching operation is performed using decalin, decane, kerosene or the like, the above-mentioned diluent is removed. In addition to being possible, it is preferable to solve the stretching imbalance at the time of stretching and to achieve a high draw ratio.

Of course, the means for removing the excess diluent from the ultra-high molecular weight polyethylene is not limited to the above method, and the method of stretching the unstretched product with a solvent such as hexane, heptane, thermal ethanol, chloroform, benzene and the like, and the stretched product of hexane, heptane In addition, by removing the excess diluent from the molded article effectively by a method of treating with a solvent such as thermal ethanol, chloroform or benzene, a stretched product having high elastic modulus and high strength can be obtained.

The stretching operation can be performed in one stage or in multiple stages of two or more stages. Although the draw ratio is also dependent on the desired molecular orientation effect, a stretching operation is generally performed so as to have a draw ratio of 5 to 80 times, in particular 10 to 50 times, and satisfactory results are obtained.

In the uniaxial stretching operation of the filament, tensile stretching may be performed between rollers having different circumferential speeds.

According to the present invention, a silanol condensation catalyst is impregnated in the molded product during or after the stretching, and then the stretched molded product is brought into contact with water for crosslinking.

As a silanol condensation catalyst, it is well-known by itself, for example, organic titanates, such as dialkylsulfacarboxylates, such as a dimethylsulfite dilaurate, a dimethylsyl diacetate, and a dimethylsyl octate, and a titanate tetrabutyl ester, naph You can use lead acid. These silanol condensation catalysts can be effectively impregnated in the fibers by contacting with the unstretched fibers or the stretched fibers in the state dissolved in the liquid medium. For example, when the stretching treatment is carried out in a liquid medium, the silanol condensation catalyst is dissolved in the stretching liquid medium, and the impregnation treatment of the silanol condensation catalyst into the molded body can be performed simultaneously with the stretching operation. In the method of the present invention, it is believed that diluents such as waxes contained in the molded fiber act to promote even impregnation of the silanol condensation catalyst into the molded body.

The amount of silanol condensation catalyst impregnated in the fiber is a so-called catalytic amount and it is difficult to define the amount directly, but in general 10 to 100% by weight, especially 25 to 75%, in the liquid medium in contact with the unstretched or stretched fiber. Satisfactory results are obtained by adding the silanol condensation catalyst in an amount of% and contacting the liquid catalyst with the molded body.

Crosslinking treatment of the stretched fiber is carried out by contacting the stretched fiber of silane graft ultra high molecular weight polyethylene impregnated with a silanol condensation catalyst with water. There is no particular restriction regarding the crosslinking treatment conditions, but generally, a long treatment time is required at a low treatment temperature, so that industrially, it is possible to perform contact with the stretched fiber and water at a temperature of 50 to 130 ° C. for 3 to 24 hours. It is advantageous. For this purpose, moisture may be applied to the stretched fiber in the form of hot water or steam. At the time of this crosslinking treatment, the stretched fibers may be placed under restraint conditions to prevent orientation relaxation, or conversely, some degree of orientation relaxation may occur under unconstrained conditions.

Further, further stretching treatment (usually three times or less) after crosslinking the stretched fiber further improves mechanical strength such as tensile strength.

According to the present invention, the silane crosslinked stretched fiber thus obtained is subjected to plasma treatment or corona discharge treatment.

Any device that is used for the treatment of llamas may be any device that generates plasma discharge such as high frequency discharge, microwave discharge, or glow discharge. As the treatment atmosphere, air, nitrogen, oxygen, argon, helium, etc. may be used alone or in combination of two or more. Among them, air or oxygen is preferable as the atmosphere. The atmospheric pressure is generally in the range of 10 ⁻⁴ to 10 Torr, in particular 10 ⁻² to 5 Torr. The treatment energy is suitably in the range of 20 to 300 W, in particular 50 to 200 W, and the treatment time is preferably 1 to 600 seconds, particularly 5 to 300 seconds.

The apparatus at the time of corona treatment may be a conventional corona discharge device, for example, a device made by Haogyo Co., but is not limited thereto. Examples of the electrode shape include a bar shape, a planar shape, and a split type. Among them, a bar electrode is preferable. The distance between the electrodes is usually 0.4-2.0 mm, preferably 0.7-1.5 mm. The treatment energy is usually in the range of 0.4W / m 2 / min-500W / m 2 / min, preferably 10W / m 2 / min-500W / m 2 / min, particularly preferably 25W / m 2 / min-200W / m 2 / min. If the treatment energy is less than 0.4 W / m 2 / min, there may be no effect of improving the adhesiveness. If the treatment energy exceeds 500 W / m 2 / min, (표면) may form on the surface, and the mechanical strength may decrease.

Reinforcing fibers used in the present invention have the above-mentioned crystal melting characteristics and surface chemical properties.

Melting | fusing point and the amount of crystal melting heat in this invention were measured by the following method.

The melting point was measured by a differential scanning calorimeter as follows. Differential scanning calorimeter used DSC type II (made by Parkin Elmer). The sample was constrained in the orientation direction by winding about 3 mg of aluminum plate of 4 mm x 4 mm, thickness, and 100 micrometers. Next, the sample wound on the aluminum plate was enclosed in the aluminum pan, and it was set as the sample for measurement. In addition, in an aluminum pan usually put in a reference holder, the same aluminum plate as that used as a sample was enclosed to obtain thermal equilibrium. First, the sample was held at 30 ° C. for about 1 minute, after which the temperature was raised to 250 ° C. at a temperature rising temperature of 10 ° C./min, and the melting point measurement at the first temperature rising was completed. Subsequently, it hold | maintained for 10 minutes in the state of 250 degreeC, and then, it temperature-falled at the temperature increase rate of 20 degree-C / min, and hold | maintained the sample for 10 minutes at 30 degreeC. Subsequently, the temperature increase of the 2nd time was heated up to 250 degreeC by the temperature increase rate of 10 degree-C / min, and the melting point measurement at the time of 2nd temperature rising (second run) was completed. At this time, the maximum value of the melting peak was taken as the melting point. In the case of appearing as a shoulder, a tangent line was drawn at the inflection point on the low temperature side of the shoulder and the inflection point on the high temperature side to make the intersection as the melting point.

In addition, it connects the point of 60 degreeC and 240 degreeC of an endothermic curve, and repairs it to the point which is 10 degreeC higher than the original crystal melting temperature (Tm) of the ultrahigh molecular weight polyethylene calculated | required as the main melting peak at the time of this straight line (baseline) and 2nd temperature rising. The low temperature side enclosed by them shall be equivalent to the original crystal melting (Tm) of ultra high molecular weight polyethylene, and the high temperature side shall be equivalent to the crystal melting (Tp) expressing the function of the molded article of the present invention. The amount of crystal melting calories was calculated by their area. The amount of heat of fusion according to the melting of Tp1 and Tp2 is also determined by the method described above, and the portion enclosed by the water line from Tm + 10 ° C. and the water line from Tm + 35 ° C. is the amount of heat of fusion according to the melting of Tp2. Was calculated in the same manner as that of the heat of fusion corresponding to the melting of Tp1.

The degree of molecular weight orientation in the molded product can be known by X-ray diffraction, birefringence, fluorescence polarization, or the like. In the case of the stretched silane crosslinked filaments of the present invention, for example, the orientation by half width, which is described in detail in Kogyo Kagaku Jakshi Vol. 39, p. 992 (1939), that is, the equation

In the formula, H ° is the half width (°) of the light intensity distribution curve on the device ring of the paratrope surface which is the strongest on the equator.

It is preferable from the viewpoint of heat resistance and mechanical properties that the molecular orientation is defined such that the degree of orientation (F) defined by is 0.90 or more, in particular 0.95 or more.

In addition, the amount of silane graft of the fiber used in the present invention is expressed in terms of Si% by weight of ultra high molecular weight polyethylene, preferably in the range of 0.01 to 5% by weight, particularly 0.035 to 3.5% by weight, from the viewpoint of heat resistance. In other words, when the graft amount is less than the above range, the crosslinking density is less than in the case of the present invention. On the other hand, when the graft amount is more than the above range, the crystallinity is lowered and both have insufficient heat resistance.

The amount of silane graft is, for example, the fiber after the silane graft is extracted for 4 hours in p-xylene at a temperature of 135 ° C to extract and remove unreacted silanes or diluents contained therein, and by weight or atomic absorption method. It can obtain | require by performing quantification of.

The reinforcing fibers of the invention are, for example, in the form of filaments and generally exhibit an elastic modulus of at least 20 Gpa, preferably at least 50 Gpa and a tensile strength of at least 1.2 GPa, preferably at least 1.5 GPa. The fineness of the short fibers is not particularly limited, but is generally in the range of 0.5 to 20 denyl, especially 1 to 12 denyl.

The reinforcing fibers of the present invention can be used not only as so-called multifilaments but also as so-called fibrillated tapes.

In the case of filament, it is processed by rope, net, cross sheet or other knitted fabric, nonwoven fabric, paper, and impregnated or laminated with polar material described later. If it is tape type, it is processed by cross sheet, rope, etc. The method of impregnation or lamination | stacking, or the method of impregnating a filament and a tape suitably and impregnating a matrix material as a staple reinforcement material etc. can be employ | adopted.

As the matrix material of the composite material, inorganic matrix materials such as ceramic materials such as cement Al ₂ O ₃ , SiO ₂ , B ₄ C, TiB ₂ , ZrB _2, such as portant cement and alma cement, phenol resins, epoxy resins, and unsaturated polyesters Thermosetting resins such as resins, diaryl phthalate resins, urethane resins, melamine resins, urea resins, nylons, polyesters, polycarbonates, polyacetars, polyvinyl chlorides, cellulose resins, polystyrenes, acryronitrile styrene copolymers Organic matrix materials, such as thermoplastic resins, etc. are mentioned. As these matrix materials, if curing temperature or molding temperature is less than Tp1 of the fiber of this invention, it can heat and bond.

On the other hand, as the polar material exceeding the Tp1 of the fiber of the present invention, a method in which an organic solvent is removed and dried after impregnating a polyolefin molded article in a solution in which a matrix material is dissolved in an organic solvent or the like can be employed.

The molding of the composite material may be performed in a molding process of a United Directional (UD) laminate, sheet molding compound (SMC), bulk molding compound (BMC), and the like as a composite material using glass fiber.

The compounding quantity of the fiber for reinforcement in a composite material can be varied widely, for example, can be in the range of 10 to 90 weight%, especially 50 to 85 weight% per composite material.

According to the present invention, there is provided a reinforcing fiber material exhibiting excellent adhesion to the matrix material in the composite while substantially retaining the excellent heat resistance and mechanical properties of the molecular orientation and silane crosslinked ultra high molecular weight polyethylene fibers.

In other words, the reinforcing fibers have significantly improved adhesion and heat resistance to the matrix material compared to conventional molded articles subjected to corona discharge treatment and the like, and the holding ratio of mechanical strength such as elastic modulus and tensile strength of the molded articles is usually 85% or more. Preferably, it is more than 90% and there is no mechanical strength deterioration. Therefore, it is combined with reinforcing fibers having such characteristics and various polar materials, such as sporting goods such as rackets, skis, fishing rods, golf clubs, jukdo, yachts, boats, sapphire boats, etc. In the case of medical materials such as leisure products, armors such as helmets, artificial joints, and dentures, mechanical strengths such as bending strength and flexural modulus are remarkably improved.

EXAMPLE

The present invention will be explained in more detail with the following examples.

Example 1

[Grafting and spinning]

Powder of ultra high molecular weight polyethylene (ultra-viscosity {η} = 6.30 dl / g): 100 parts by weight of vinyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.): 10 parts by weight and 2,5-dimethyl-2,5- Di (tert-Butylperoxy) hexane (Nion Shushing agent: trade name Perhexa 25B): Powder of paraffin wax (Nihon Seroze, trade name Lubox 1266, per 100 parts by weight of ultra high molecular weight polyethylene after uniformly mixing 0.1 parts by weight). Melting point = 69 ° C.): 370 parts by weight was added and mixed to obtain a mixture. The mixture was then melt kneaded using a screw extruder (screw diameter = 20 mm, L / D = 25) at a set temperature of 200 ° C., followed by spinning the melt into a die with an orifice diameter of 2 mm to complete the silane graft. do. The spun fiber was cooled and solidified with air at room temperature in an air gap of 180 cm to give an unstretched ultra high molecular weight polyethylene graft fiber. The graft ratio at the time of spinning was 36.4. Moreover, the winding speed at this time was 90 m / min.

[Quantification of Silane Graft Amount]

About 8 g of the unstretched graft fiber prepared by the above method was dissolved in p-xylene 200CC heated and held at 135 ° C. Subsequently, ultra-high molecular weight polyethylene was precipitated in excess hexane at room temperature to remove paraffin wax and unreacted silane compound. Then, the graft amount calculated | required by Si weight% by the weight method was 0.58 weight%.

[Extension]

The grafted unstretched fiber spun from the ultrahigh molecular weight polyethylene mixture by the above method was stretched under the following conditions to obtain an orientation stretched fiber. Three godrols were used to perform two-stage stretching in an n-decane-based stretching vessel. At this time, the temperature in the 1st drawing tank was 110 degreeC, the temperature in the 2nd drawing tank was 120 degreeC, and the effective length of the tank was 50 cm, respectively. At the time of stretching, the rotation speed of the first high dextrol was 0.5 m / min, and the rotation speed of the third high dextrol was changed to obtain a fiber having a desired draw ratio. In addition, the rotation speed of the second godecrol was selected by the enemy within the range of stable stretching. However, the draw ratio was calculated by calculating the rotation ratio between the first and third godecrol.

The obtained fiber was dried at room temperature under constant pressure, and it was set as the stretched ultrahigh molecular weight polyethylene silane graft fiber.

[Impregnation of crosslinking catalyst]

When crosslinking the oriented fibers of the silane compound graft ultra high molecular weight polyethylene prepared by the above method, paraffin wax is prepared by using a mixture of n-decane and n-decane in the same amount as the fruit in the second stretching bath during stretching. At the same time as distillate dilaurate was impregnated into the fiber. The obtained fiber was dried at room temperature under reduced pressure until the decane odor disappeared.

[Bridge]

After that, the fibers were left standing in boiling water to complete the crosslinking.

[Measurement of gel fraction]

About 0.4 g of the silane crosslinked stretch ultrahigh molecular weight polyethylene fiber obtained by the above method was introduced into a triangular flask equipped with a condenser containing 200 ml of paraxylene and stirred in a boiling state for 4 hours. The insolubles were then filtered through a 300 mesh stainless steel mesh. After drying under reduced pressure at 80 ° C., the basis weight was used to determine the weight of the insoluble matter. The gel fraction was calculated by the following equation.

The gel fraction of the prepared sample was 51.4%.

Tensile modulus, tensile strength, and elongation at break were measured at room temperature (23 ° C) using an Instron universal testing machine type 1123 (manufactured by Instron). The sample length between clamps was 100 mm, and the tensile velocity was 100 mm / min. However, the tensile modulus is the initial modulus. The fiber cross-sectional area required for the calculation was obtained by measuring the weight and length of the fiber with a polyethylene density of 0.968 g / cm 3.

The physical properties of the silane crosslinked stretched ultra high molecular weight polyethylene fiber thus obtained are shown in Table 1.

TABLE 1

In addition, the original crystal melting temperature (Tm) of the ultra-high molecular weight polyethylene, which is obtained as the main melting peak at the second temperature rise, is 132.4 ° C, and the ratio of the heat of fusion according to Tp to the heat of fusion and the heat of fusion according to Tp1. The percentages of fusion calories were 72% and 23%, respectively. At this time, the main one of Tp2 was 151.1 ° C and the main one of Tp1 was 226.6 ° C.

[Evaluation of Creep Characteristics]

The creep test was performed at 1 cm of sample length and 70 degreeC of atmosphere temperature using the thermal stress distortion measuring apparatus TMA / SS10 (made by Seiko Denshi Kogyo Co., Ltd.).

The result at 30% load of breaking load is shown in FIG. It can be seen that the silane crosslinked stretched high molecular weight polyethylene fiber (sample-1) prepared in this example has significantly improved creep characteristics in all cases compared with the uncrosslinked stretched ultrahigh molecular weight polyethylene fiber (sample-2).

Table 2 shows the elongation at 1 minute, 2 minutes, and 3 minutes immediately after the load by the creep test performed at a load corresponding to 50% of the breaking load at room temperature at an ambient temperature of 70 ° C.

TABLE 2

Strength retention rate after thermal history

The thermal history test was done by leaving in a gear oven (Perfect oven: Dahaisei Corporation). The sample was bent by turning a plurality of pulleys on both ends of the stainless steel frame with a length of about 3 m to be fixed to both ends of the sample. At this time, both ends of the sample were fixed so that the sample would not sag, and no tension was actively applied to the sample. The results are shown in Table 3.

TABLE 3

[Plasma treatment]

The obtained molecular orientation and silane crosslinked ultra-high molecular weight polyethylene filament (1000 degree of dendritic / 100) was produced by using a high frequency plasma processing apparatus manufactured by SAMCO INTERNATIONAL CO., LTD. Processed in seconds. An electron micrograph of the fiber surface before the plasma treatment is shown in FIG. 4, and an electron micrograph of the fiber surface after the plasma treatment is shown in FIG.

Fibrous physical properties after the treatment were 1.70 GPa in strength (holding rate of 100%) and 52.1 GPa in elasticity rate (holding rate of 94.7%).

In the ESCA analysis of the fiber surface before plasma treatment, the number of oxygen atoms per 100 carbon atoms was less than 6, but the number of oxygen atoms per 100 carbon atoms was increased to 22 by plasma treatment.

[Production of Composite Material]

Two kinds of epoxy resins (EPOMIK ^(R) R-301 M 80 and R-140, Mitsui Sekiyu Chemical Co., Ltd. ⁾ dicyanodiamide, p-chlorophenyl-1, 1-dimethylurea and dimethylholmeamide were impregnated into a resin mixed at a weight ratio of 87.5 / 30/5/5/25, respectively, and dried at 100 ° C for 10 minutes to prepare a prepreg and laminating it for 1 hour at 100 ° C. The press was molded and a one-way laminate was made. Next, the bending strength and the flexural modulus of the laminate were measured. (JIS K691) The results are shown in Table 4.

In addition, the fiber weight per whole composite material was 79%.

Example 2

The filaments of the molecular orientation and silane crosslinked ultrahigh molecular weight polyethylene used in Example 1 were treated using nitrogen as the treatment gas using the same apparatus as in Example 1. Using this as a sample, a laminated plate was prepared under the same conditions as in Example 1. The results are shown in Table 4.

The result of electron microscope observation of the surface of a filament was the same as FIG. The fiber strength after the treatment was 1.68 GPa (holding rate 99.4%), and the elastic modulus was 54.0 GPa (holding rate 98.2%).

In the analysis by ESCA, the number of oxygen atoms per 100 carbon atoms was 10.

Example 3

The filaments of the molecular orientation and silane crosslinked ultra high molecular polyethylene used in Example 1 were set to 1.0 mm nationwide using a bar electrode in a corona discharge treatment apparatus manufactured by Ogyo Co., Ltd., and treated at an irradiation dose of 75 W / m 2 / min. The result of electron microscope observation of the surface of a filament was the same as FIG.

The fiber after the treatment had a strength of 1.69 GPa (holding rate of 99.4%) and an elastic modulus of 53.0 GPa (holding rate of 96.4%). In addition, in the measurement by ESPA, the number of oxygen atoms added was 17 per C100. Using this as a sample, a laminated plate was made under the same conditions as in Example 1. The results are shown in Table 4.

Comparative Example 1

The red worm board was created on the same conditions as Example 1, using the same silane crosslinking high strength high elasticity polyethylene fiber as Example 1, without making any sample. The results are shown in Table 4.

TABLE 4

* The number of oxygen atoms per 100 carbon atoms.

Claims (6)

Intrinsic crystal melting temperature (Tm) of ultra-high molecular weight polyethylene obtained by surface treatment of molecular orientation and silane-crosslinked ultra high molecular weight polyethylene, which is obtained as the main melting peak at the second elevated temperature when measured by a differential scanning calorimeter under confinement. It has at least two crystal melting peaks (Tp) at a temperature higher than at least 10 ° C, and the amount of heat of fusion corresponding to this crystal melting peak (Tp) per heat of melting is 50% or more and the temperature range Tm + 35 ° C to Tm + 120 ° C. The total amount of heat of fusion according to the high temperature side melting peak (Tp1) in the film is not less than 5% per heat of melting, and this fiber is measured by electron spectroscopy pore chemical analysis (ESCA) of at least 8 per 100 carbon atoms. A reinforcing fiber material having improved adhesion, characterized by having a surface having a composition having two oxygen atoms. According to claim 1, wherein the surface-treated fibers are grafted silane compound to the ultimate viscosity {η} of 5 dl / g or more polyethylene at 135 ℃ decaline solvent, and then formed into a fibrous form, stretched and then grafted silane A fiber material for reinforcement, which is a fiber obtained by subjecting a molecular orientation and a silane crosslinked fiber obtained by crosslinking a compound to a plasma or corona discharge treatment. The reinforcing fiber material according to claim 1, wherein said surface treated fiber has an orientation degree (F) of 0.90 or more. The reinforcing fiber material according to claim 1, wherein the surface treated fiber has an elastic modulus of 20 GPa or more and a tensile strength of 1.2 GPa or more. The reinforcing fiber material according to claim 1, wherein the surface treated fiber has a crack width in a surface orientation direction of less than 0.1 mu m. The reinforcing fiber material according to claim 1, wherein the surface-treated fiber has a surface composition having 10 or more oxygen atoms per 100 carbon atoms as measured by ESCA.

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